Always and Never
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See also: For a High Yield,
Rules of Thumb
- Pay attention.
Many cases of experimental failure are repercussions
resulting from inattention, or from
Leaving the Lab
while a reaction is underway.
When you start an experiment, the clock starts ticking.
Make sure everything is ready beforehand.
- Monitor regularly.
Many students do not track their experiment closely enough.
- When washing with aqueous bicarbonate, vent the separatory funnel
often to prevent pressure buildup from evolving carbon dioxide.
- Wash the organic layer with brine last.
- Copy or print the entire journal article,
not just the pages you need.
- Allow compounds from the refrigerator to warm to RT
before opening them.
- Cospot your reaction on TLC.
- Check to make sure your starting compounds are pure.
- Store intermediates in the refrigerator or freezer.
- Use tared flasks.
- Stir reactions vigorously.
- TLC a reaction as soon as it is begun.
- Keep your rotovap bump trap clean.
- Break the vacuum before turning off the vacuum source.
- Put a flask under your separatory funnel before pouring anything into it.
- Use a funnel.
- Check to make sure your flask is clamped firmly before spinning the rotary evaporator.
- Titrate n-BuLi prior to using.
- Leave your experiment:
Leaving the Lab and First Time Through.
Put your compound under high vacuum unless you know it won't evaporate.
Throw away any fractions from a column before you have an NMR of your product.
Throw away the aqueous layer of an extraction before you have an
NMR of your product.
- Pour neat compound- use a pipette.
Fill round-bottom flasks more than half full-(reactions,
distillations, and rotoevaporation)
- Heat a closed system without venting.
Save a sample of the starting material when running a reaction
for the first time.
- Save a sample of the crude product
when doing column chromatography.
- Work up the reaction
immediately after quenching it.
Notice if your reaction is becoming hot unexpectedly during
any step, and cool the flask with an ice bath.
Maintain a homogeneous solution.
Maintain the correct temperature
- If a solid crashes out of
solvent at any point, filter it and analyze the
solid and the filtrate.
- If the compound
is not volatile, put it on a high vacuum line
for 10-20 minutes after rotoevaporation (and before NMR)
to remove residual solvent.
- Designate a notebook
for literature search information. Record the date,
the search parameters, what references were found, and
which ones you looked up.
Tips for Planning an Experiment
Tips for Spectroscopy
Tips for Record-keeping
Kende's 20 Points